1. Field of the Invention
The present invention relates to a collimator and an inspecting system using the same, and more particularly, to a collimator which can realize an ultra-low-dose radiation inspecting system by reducing the number of projection views without adjusting the power of a radiation source by adjusting an area that is to be irradiated with radiation and an inspecting system using the collimator.
2. Description of the Related Art
Medical devices that take an image of a body part of a patient by using radiation having penetrating nature are being widely used. However, such medical devices adversely affect patients due to a large amount of radiation exposure. For example, radiation can cause DNA changes, cancer, nausea, headaches, etc. depending on the radiation dose. Therefore, a collimator is used to reduce the amount of radiation exposure.
FIG. 1 is a diagram illustrating a conventional radiographic device.
Referring to FIG. 1, the conventional radiographic device includes a collimator 5 between a radiation source 3 which irradiates radiation and a sensor 4 which senses the radiation. The radiation may be incident on an object through the collimator 5. Here, an area to be irradiated with the radiation is adjusted by the collimator 5. Radiation that fails to pass through a gap of the collimator 5 is absorbed by blades made of a high band-gap material. That is, radiation adjusted by the collimator 5 is incident on an object, and the radiation that passes through the object is sensed by the sensor 4. The detected signal is processed by a processor and generated as an image.
In the conventional radiographic device, however, the collimator 5 can only adjust the beam width of radiation in order to limit a field of view (FOV).
Among radiographic devices, computed tomography (CT) technology has been continuously developed with an am to reduce the time required to obtain an image. In particular, the enhancement of the rotation speed of a CT gantry and the application of a multi-slice detector have greatly contributed to a reduction in the time required to obtain an image. However, the enhancement of the rotation speed of the CT gantry has reached the limit due to the weight of the gantry, and an increase in the number of multi-slice detectors generates a cone beam artifact.
Recently, the safety of CT imaging has been questioned due to radiation exposure. Therefore, research is being actively conducted to reduce the amount of radiation to which a patient is exposed. Some examples include a research on a low-dose CT system using tube current and a research on an image reconstruction system based on a compressive sensing theory. However, these researches have problems such as the degradation of projection data quality due to noise and the fast adjustment of the power of x-rays, respectively.
The present invention is focused on an image reconstruction system based on the compressive sensing theory among many researches on ultra-low-dose CT systems. A lot of research results have already showed that satisfactory image reconstruction is possible in a low-dose environment based on the compressive sensing theory even if a small number of projection views are used. In this case, however, the power of an x-ray source should be turned ON or OFF. Considering that the x-ray source rotates once per approximately 0.3 seconds in the case of diagnostic CT, there remains a technical challenge of adjusting the power of the x-ray source faster than the rotation speed of a high-speed gantry.